1. Field of the Invention
The present invention relates to an automatic accompaniment apparatus which is suitable for the electronic musical instrument such as the electronic piano.
2. Prior Art
As known well, the recent model of the electronic piano provides the automatic accompaniment apparatus. This automatic accompaniment apparatus is provided to assist the chord performance and bass performance. Herein, on the basis of the detection result of detecting the chord type and root of the performed chord, the chord and bass sounds are automatically generated at the predetermined timings. Particularly, there is developed an automatic accompaniment apparatus which plays the automatic accompaniment on the basis of the subharmonic chord (or fractional chord) to be detected. Incidentally, this subharmonic chord is defined as the chord which includes the chord note (or chord constituent note) and bass note each having the different root.
On the basis of plural pieces of pitch information which are produced responsive to the key-depression made by the performer, the above-mentioned automatic accompaniment apparatus detects the chord root of the subharmonic chord so as to compute the bass interval corresponding to the chord root and subharmonic chord. As a result, chord notes and bass notes of the subharmonic chord are to be sounded. This kind of technique is disclosed in Japanese Patent Laid-Open Publication No. 2-179690, for example.
Meanwhile, the above-mentioned conventional automatic accompaniment apparatus provides a pattern detection table, so that the chord can be detected by referring to this table. In this pattern detection table, each of the chord types each represented by twelve notes (e.g., C, C#, D, . . . , A#, B) is represented by 12-bit pattern data (hereinafter, referred to as chord pattern data), which are stored in the memory by the table-type format. Herein, data representing the mixture of the chord notes and bass notes are registered in this pattern detection table. In addition, only the simple subharmonic chords are registered in this table.
Therefore, when detecting the chord by use of the pattern detection table, the chord pattern is merely searched without distinguishing between the chord note and bass note in the chord to be designated. Therefore, the conventional apparatus forces to match the actually generated chord pattern with one of the limited number of the subharmonic chords registered in the table, thus regarding it as the detection result. For this reason, there is a drawback in that the accurate search cannot be made with respect to the subharmonic chords. In order to eliminate such drawback, a large number of tables must be provided to register complex patterns of the subharmonic chords. However, this increase the memory capacity which is required to store those tables.